It's easy to trigger avalanches right now in some locations. Conditions are expected to deteriorate further before Christmas. Play safe.
Confidence
Fair - Due to the number of field observations
Weather Forecast
Expect moderate snowfall on Tuesday (5-20cm, mostly late in the day) with strong south-westerly winds and freezing level around 500m. A cooler northwest flow may bring light snow or flurries on Wednesday and Thursday.
Avalanche Summary
Several storm slabs were triggered naturally on Sunday and a helicopter remotely triggered a size 2 slab at treeline in the south of the region.
Snowpack Summary
Storm snow has built up above variable old surfaces including large fragile surface hoar crystals, a crust and/or facets. This layer has the potential for remote triggering and wide propagations. Winds may have built wind slabs and cornices on lee slopes. A thick rain crust with facets from early November is buried over 1 m down and may still be reactive in isolated areas. Recent storm snow amounts are quite variable across the region. If you're in the south, have look at the North Columbia bulletin too.
Problems
Storm Slabs
Storm Slab avalanches are the release of a cohesive layer (a slab) of new snow that breaks within new snow or on the old snow surface. Storm-slabs typically last between a few hours and few days (following snowfall). Storm-slabs that form over a persistent weak layer (surface hoar, depth hoar, or near-surface facets) may be termed Persistent Slabs or may develop into Persistent Slabs.
Deep Persistent Slabs
Deep Persistent Slab avalanches are the release of a thick cohesive layer of hard snow (a slab), when the bond breaks between the slab and an underlying persistent weak layer deep in the snowpack. The most common persistent weak layers involved in deep, persistent slabs are depth hoar or facets surrounding a deeply buried crust. Deep Persistent Slabs are typically hard to trigger, are very destructive and dangerous due to the large mass of snow involved, and can persist for months once developed. They are often triggered from areas where the snow is shallow and weak, and are particularly difficult to forecast for and manage.